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Fencer Vulns
medium 5.5

CVE-2022-49394 json

blk-iolatency: Fix inflight count imbalances and IO hangs on offline

published 2025-02-26 20 mo ago modified 2026-06-17 4 mo ago also EUVD-2022-54835

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

blk-iolatency: Fix inflight count imbalances and IO hangs on offline

iolatency needs to track the number of inflight IOs per cgroup. As this tracking can be expensive, it is disabled when no cgroup has iolatency configured for the device. To ensure that the inflight counters stay balanced, iolatency_set_limit() freezes the request_queue while manipulating the enabled counter, which ensures that no IO is in flight and thus all counters are zero.

Unfortunately, iolatency_set_limit() isn't the only place where the enabled counter is manipulated. iolatency_pd_offline() can also dec the counter and trigger disabling. As this disabling happens without freezing the q, this can easily happen while some IOs are in flight and thus leak the counts.

This can be easily demonstrated by turning on iolatency on an one empty cgroup while IOs are in flight in other cgroups and then removing the cgroup. Note that iolatency shouldn't have been enabled elsewhere in the system to ensure that removing the cgroup disables iolatency for the whole device.

The following keeps flipping on and off iolatency on sda:

echo +io > /sys/fs/cgroup/cgroup.subtree_control while true; do mkdir -p /sys/fs/cgroup/test echo '8:0 target=100000' > /sys/fs/cgroup/test/io.latency sleep 1 rmdir /sys/fs/cgroup/test sleep 1 done

and there's concurrent fio generating direct rand reads:

fio --name test --filename=/dev/sda --direct=1 --rw=randread \ --runtime=600 --time_based --iodepth=256 --numjobs=4 --bs=4k

while monitoring with the following drgn script:

while True: for css in css_for_each_descendant_pre(prog['blkcg_root'].css.address_of_()): for pos in hlist_for_each(container_of(css, 'struct blkcg', 'css').blkg_list): blkg = container_of(pos, 'struct blkcg_gq', 'blkcg_node') pd = blkg.pd[prog['blkcg_policy_iolatency'].plid] if pd.value_() == 0: continue iolat = container_of(pd, 'struct iolatency_grp', 'pd') inflight = iolat.rq_wait.inflight.counter.value_() if inflight: print(f'inflight={inflight} {disk_name(blkg.q.disk).decode("utf-8")} ' f'{cgroup_path(css.cgroup).decode("utf-8")}') time.sleep(1)

The monitoring output looks like the following:

inflight=1 sda /user.slice inflight=1 sda /user.slice ... inflight=14 sda /user.slice inflight=13 sda /user.slice inflight=17 sda /user.slice inflight=15 sda /user.slice inflight=18 sda /user.slice inflight=17 sda /user.slice inflight=20 sda /user.slice inflight=19 sda /user.slice <- fio stopped, inflight stuck at 19 inflight=19 sda /user.slice inflight=19 sda /user.slice

If a cgroup with stuck inflight ends up getting throttled, the throttled IOs will never get issued as there's no completion event to wake it up leading to an indefinite hang.

This patch fixes the bug by unifying enable handling into a work item which is automatically kicked off from iolatency_set_min_lat_nsec() which is called from both iolatency_set_limit() and iolatency_pd_offline() paths. Punting to a work item is necessary as iolatency_pd_offline() is called under spinlocks while freezing a request_queue requires a sleepable context.

This also simplifies the code reducing LOC sans the comments and avoids the unnecessary freezes which were happening whenever a cgroup's latency target is newly set or cleared.

Patch / fix

  • Linux Linux 4.19.247, 4.21, 5.4.198, 5.10.121, 5.15.46, 5.17.14, 5.18.3, 5.19
  • linux Debian 14, Debian 13, Debian 12 5.18.5-1

debian advisories DEBIAN-CVE-2022-49394

  • linux Ubuntu 20.04 LTS 5.4.0-126.142
  • linux Ubuntu 22.04 LTS 5.15.0-47.51
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1085.92
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1019.23
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1089.97
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1017.23
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1015.18
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1033.37

ubuntu advisories UBUNTU-CVE-2022-49394

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-162.6.1.el9_1
  • perf RHEL 9 5.14.0-162.6.1.el9_1
  • bpftool RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-core RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-tools RHEL 9 5.14.0-162.6.1.el9_1
  • python3-perf RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-modules RHEL 9 5.14.0-162.6.1.el9_1
  • kernel-zfcpdump RHEL 9 5.14.0-162.6.1.el9_1

red hat advisories RHSA-2022:8267

  • kernel-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.201.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.201.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.201.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.201.1.150300.18.120.1
  • kernel-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.100.1

suse advisories SUSE-SU-2025:1263-1SUSE-SU-2025:1241-1SUSE-SU-2025:1194-1SUSE-SU-2025:1183-1SUSE-SU-2025:1176-1SUSE-SU-2025:1027-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-49394 updated cvss 5.5

kernel: blk-iolatency: Fix inflight count imbalances and IO hangs on offline

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat CodeReady Linux Builder (v. 9) kernel-debuginfo-common-s390x 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-x86_64 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-aarch64 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-ppc64le 5.14.0-162.6.1.el9_1 Red Hat Enterprise Linux AppStream (v. 9) perf 5.14.0-162.6.1.el9_1, kernel-devel-matched 5.14.0-162.6.1.el9_1, kernel-debug-devel-matched 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-s390x 5.14.0-162.6.1.el9_1, kernel-zfcpdump-devel-matched 5.14.0-162.6.1.el9_1, kernel-debuginfo-common-x86_64 5.14.0-162.6.1.el9_1, +2 more Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-162.6.1.el9_1, bpftool 5.14.0-162.6.1.el9_1, kernel-core 5.14.0-162.6.1.el9_1, kernel-tools 5.14.0-162.6.1.el9_1, python3-perf 5.14.0-162.6.1.el9_1, kernel-modules 5.14.0-162.6.1.el9_1, +14 more
    fixed: vendor fix RHSA-2022:8267
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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